Various forms of convertible sofa beds have been heretofore designed, but most involve relatively complex supporting linkage systems for a foldable mattress supporting spring structure and require the utilization of a mattress structure in addition to the seat cushion of the sofa. Further, most conventional convertible sofa beds utilize a complex supportive linkage system for the mattress spring portion thereof which are extremely heavy and utilize counterbalance springs which tend to project the foldable portions of the convertible sofa beds toward their fully extended positions after having been at least partially opened.
Examples of various forms of convertible sofa bed and chair structures including some of the basic structural features of the instant invention are disclosed in U.S. Pat. Nos. 1,266,691, 2,328,254, 2,335,870, 2,681,691, 2,687,766, 2,878,491, 2,911,032, 3,107,366 and 3,198,576.